Broken Souls and Bones by L.J. Andrews

Lyra Bien intended to live a quiet life to avoid the attention of the magic-obsessed king in the fortress of Stonegate. Until Roark Ashwood—the prince’s silent guard and rumored killer for the crown—invades her village and uncovers the truth behind the silver scars in her eyes. To save her best friend from death, she’s forced to reveal her abilities, and is immediately claimed by the crown as the next melder.

To be the King’s melder is to be revered and feared in equal measures, but above all it is a slow death sentence. Lyra is determined to find a way to free herself and her friends from bondage. But first she must get more information from the silent, brooding sentry who first took her captive: Roark.

As Lyra gets closer to Roark, she soon learns he’s nothing like she assumed—and in fact everything she needs. The more they work as allies, the harder it becomes to ignore the growing passion between them. After a sinister truth is revealed, Roark and Lyra must choose to stand against all they know, or accept their dark destiny.